Rechargeable battery systems for electric vehicles with purely electrical drive and for hybrid vehicles and vehicles with fuel cell drive are the subject of current research. At present, in the said types of vehicle lithium-ion batteries are preferably used, which are distinguished by a high energy density and an only weakly developed undesired memory effect. The capability of a rechargeable battery to supply reliably with electrical energy various electrical consumers installed in motor vehicles depends to a considerable extent on the thermal conditions prevailing in the environment of the battery.
Thermally well-defined environmental conditions are of great importance for a reliable and interference-free operation of the batteries—this applies not only for the said lithium-ion-based batteries, but generally for any rechargeable battery systems. In view of the considerable temperature fluctuations occurring for instance in a motor vehicle under normal operating conditions, this means that these fluctuations must be compensated by suitable temperature control devices coupled thermally to the battery, in order to keep the environmental temperature of the battery—and therefore also the temperature of the battery itself—within a temperature interval specified by the manufacturer.
Against this background, cooling devices are known from the prior art with metallic cooling plates, which contains a cooling duct structure, which in turn is able to be flowed through by a cooling means. The desired cooling effect is achieved by thermal interaction of the cooling means with the battery which is to be temperature-controlled. A heating function can also be integrated into the cooling device in a suitable manner, which heating function may be realized for example by means of electrical PTC heating elements.
As both the housing of the battery which is to the temperature-controlled and also the cooling plates are produced from a metal, the risk exists in conventional cooling devices that undesired electrical creepage currents can form between the housing of the battery and the cooling plates. In extreme cases, for instance in the formation of an electrical short circuit between battery and cooling device, such high electrical currents can even flow that they lead to a damage to the battery or to the cooling device. Independently thereof, with the use of metals as material system for the cooling plates, also the minimum requirements with regard to diffusion resistance of the cooling device are often not fulfilled.
It is therefore known from the prior art to arrange at the interface between cooling plate of the cooling device and the battery housing of the battery an electrical insulation layer of an electrically insulating material with high thermal conductivity. In particular, the use of a film of plastic or a silicone layer is known.
Against this background, DE 10 2008 059 952 B4 discloses a battery with several battery cells and a generic cooling device for cooling the battery cells. A metallic base body of the cooling device is equipped with an electrically insulating insulation layer. This is an injection-moulded layer of a plastic injected onto the base body.
The not insignificant effort in terms of process technology for applying such an electrical insulation onto the cooling plate of the cooling device or onto the battery housing of the battery which is to be cooled proves to be a disadvantage in the production of such electrical insulation layers. This leads typically to a considerable cost increase in the production of the cooling device.